The present invention relates to oceanographic sediment-collecting instruments and, in particular, to means for collecting the pore water of deep-sea sedimentary deposits.
During recent years it has become evident that great care must be exercised in the collection and processing of samples of deep-sea sediment pore water. For example, significant concentration changes occur when pore water is removed from core samples at a temperature other than the in-situ temperature. Also, there is the possibility that smaller concentration changes may be due to the effect of pressure on the ion-exchange equilibrium. Usual sampling procedures apparently have precluded thorough investigation of this latter possibility.
The sampling problem is especially serious when the sample is to be used to analyze its dissolved gases. Degassing, bubble formation and atmospheric contamination can and do occur during core recovery and processing and the apparent inability to control these factors probably is the major reason why trace gas analysis of marine sediments still is in its infancy. Previous studies of dissolved gases in sediments have involved core recovery and direct extraction of gases from sediment slurries, see Koyama, (1953) Measurement and Analysis of Gases in Sediment, J. Earth Sci., Nagoya University, 1, 107-118 and Emery and Hogan (1958), Gases in Marine Sediments, Bull. Am. Assoc. Petrol. Geol., 42, 2174-2188. Other procedures involve the initial separation of the pore fluid by a filter press prior to extraction (see Reeburgh) (1968, 1969), Observation of Gases in Chesapeake Bay Sediments, Limnol. Oceanogr., 14, 368-375. Both procedures have utilized a pure gas atmosphere during sample manipulation to eliminate atmospheric contamination and, in doing so, have precluded analyses for that particular gas. Also, despite the use of rather elaborate procedures, the published data suggests sample loss and contamination as well as large variations in replicate analyses that could be the result of sampling problems.
Ideally, the pore fluid should be separated from the solid phase and encapsulated in-situ, thereby eliminating exchange reactions with the sediment and contamination or loss of gases during the recovery and processing. Wilson, Sayles and Mangelsdorf, Jr. (1972) in Trans. Am. Geophys. UN., 53, 529 disclose "An in-situ Filter for Taking Samples of Interstitial Water from Marine Sediments." This sampler stores the fluid in capillary tubing to preserve the filtered fluid in time sequence. Also, it is limited to sampling depths of about 150 centimeters or less below the sediment water interface and, in general, its construction presents other difficulties which have restricted its use.